#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import copy

from heat.common import environment_format
from heat.common import exception
from heat.common.i18n import _
from heat.common import timeutils as iso8601utils
from heat.engine import attributes
from heat.engine import function
from heat.engine import properties
from heat.engine import rsrc_defn
from heat.engine import scheduler
from heat.engine import stack_resource
from heat.scaling import template


(SCALED_RESOURCE_TYPE,) = ('OS::Heat::ScaledResource',)


class InstanceGroup(stack_resource.StackResource):

    PROPERTIES = (
        AVAILABILITY_ZONES, LAUNCH_CONFIGURATION_NAME, SIZE,
        LOAD_BALANCER_NAMES, TAGS,
    ) = (
        'AvailabilityZones', 'LaunchConfigurationName', 'Size',
        'LoadBalancerNames', 'Tags',
    )

    _TAG_KEYS = (
        TAG_KEY, TAG_VALUE,
    ) = (
        'Key', 'Value',
    )

    _ROLLING_UPDATE_SCHEMA_KEYS = (
        MIN_INSTANCES_IN_SERVICE, MAX_BATCH_SIZE, PAUSE_TIME
    ) = (
        'MinInstancesInService', 'MaxBatchSize', 'PauseTime'
    )

    _UPDATE_POLICY_SCHEMA_KEYS = (ROLLING_UPDATE,) = ('RollingUpdate',)

    ATTRIBUTES = (
        INSTANCE_LIST,
    ) = (
        'InstanceList',
    )

    properties_schema = {
        AVAILABILITY_ZONES: properties.Schema(
            properties.Schema.LIST,
            _('Not Implemented.'),
            required=True
        ),
        LAUNCH_CONFIGURATION_NAME: properties.Schema(
            properties.Schema.STRING,
            _('The reference to a LaunchConfiguration resource.'),
            required=True,
            update_allowed=True
        ),
        SIZE: properties.Schema(
            properties.Schema.INTEGER,
            _('Desired number of instances.'),
            required=True,
            update_allowed=True
        ),
        LOAD_BALANCER_NAMES: properties.Schema(
            properties.Schema.LIST,
            _('List of LoadBalancer resources.')
        ),
        TAGS: properties.Schema(
            properties.Schema.LIST,
            _('Tags to attach to this group.'),
            schema=properties.Schema(
                properties.Schema.MAP,
                schema={
                    TAG_KEY: properties.Schema(
                        properties.Schema.STRING,
                        required=True
                    ),
                    TAG_VALUE: properties.Schema(
                        properties.Schema.STRING,
                        required=True
                    ),
                },
            )
        ),
    }

    attributes_schema = {
        INSTANCE_LIST: attributes.Schema(
            _("A comma-delimited list of server ip addresses. "
              "(Heat extension).")
        ),
    }
    rolling_update_schema = {
        MIN_INSTANCES_IN_SERVICE: properties.Schema(properties.Schema.NUMBER,
                                                    default=0),
        MAX_BATCH_SIZE: properties.Schema(properties.Schema.NUMBER,
                                          default=1),
        PAUSE_TIME: properties.Schema(properties.Schema.STRING,
                                      default='PT0S')
    }
    update_policy_schema = {
        ROLLING_UPDATE: properties.Schema(properties.Schema.MAP,
                                          schema=rolling_update_schema)
    }

    def __init__(self, name, json_snippet, stack):
        """
        UpdatePolicy is currently only specific to InstanceGroup and
        AutoScalingGroup. Therefore, init is overridden to parse for the
        UpdatePolicy.
        """
        super(InstanceGroup, self).__init__(name, json_snippet, stack)
        self.update_policy = self.t.update_policy(self.update_policy_schema,
                                                  self.context)

    def validate(self):
        """
        Add validation for update_policy
        """
        super(InstanceGroup, self).validate()

        if self.update_policy:
            self.update_policy.validate()
            policy_name = self.update_policy_schema.keys()[0]
            if self.update_policy[policy_name]:
                pause_time = self.update_policy[policy_name][self.PAUSE_TIME]
                if iso8601utils.parse_isoduration(pause_time) > 3600:
                    raise ValueError('Maximum PauseTime is 1 hour.')

    def validate_launchconfig(self):
        # It seems to be a common error to not have a dependancy on the
        # launchconfiguration. This can happen if the the actual resource
        # name is used instead of {get_resource: launch_conf} and no
        # depends_on is used.

        conf_refid = self.properties.get(self.LAUNCH_CONFIGURATION_NAME)
        if conf_refid:
            conf = self.stack.resource_by_refid(conf_refid)
            if conf is None:
                raise ValueError(_('%(lc)s (%(ref)s)'
                                   ' reference can not be found.')
                                 % dict(lc=self.LAUNCH_CONFIGURATION_NAME,
                                        ref=conf_refid))
            if self.name not in conf.required_by():
                raise ValueError(_('%(lc)s (%(ref)s)'
                                   ' requires a reference to the'
                                   ' configuration not just the name of the'
                                   ' resource.') % dict(
                                       lc=self.LAUNCH_CONFIGURATION_NAME,
                                       ref=conf_refid))

    def get_instance_names(self):
        """Get a list of resource names of the instances in this InstanceGroup.

        Failed resources will be ignored.
        """
        return [r.name for r in self.get_instances()]

    def get_instances(self):
        """Get a list of all the instance resources managed by this group.

        Sort the list of instances first by created_time then by name.
        """
        resources = []
        if self.nested():
            resources = [resource for resource in self.nested().itervalues()
                         if resource.status != resource.FAILED]
        return sorted(resources, key=lambda r: (r.created_time, r.name))

    def _environment(self):
        """Return the environment for the nested stack."""
        return {
            environment_format.PARAMETERS: {},
            environment_format.RESOURCE_REGISTRY: {
                SCALED_RESOURCE_TYPE: 'AWS::EC2::Instance',
            },
        }

    def handle_create(self):
        """Create a nested stack and add the initial resources to it."""
        self.validate_launchconfig()
        num_instances = self.properties[self.SIZE]
        initial_template = self._create_template(num_instances)
        return self.create_with_template(initial_template, self._environment())

    def check_create_complete(self, task):
        """
        When stack creation is done, update the load balancer.

        If any instances failed to be created, delete them.
        """
        done = super(InstanceGroup, self).check_create_complete(task)
        if done:
            self._lb_reload()
        return done

    def handle_update(self, json_snippet, tmpl_diff, prop_diff):
        """
        If Properties has changed, update self.properties, so we
        get the new values during any subsequent adjustment.
        """
        if tmpl_diff:
            # parse update policy
            if 'UpdatePolicy' in tmpl_diff:
                up = json_snippet.update_policy(self.update_policy_schema,
                                                self.context)
                self.update_policy = up

        if prop_diff:
            self.properties = json_snippet.properties(self.properties_schema,
                                                      self.context)

            # Replace instances first if launch configuration has changed
            self._try_rolling_update(prop_diff)

            # Get the current capacity, we may need to adjust if
            # Size has changed
            if self.SIZE in prop_diff:
                inst_list = self.get_instances()
                if len(inst_list) != self.properties[self.SIZE]:
                    self.resize(self.properties[self.SIZE])

    def _tags(self):
        """
        Make sure that we add a tag that Ceilometer can pick up.
        These need to be prepended with 'metering.'.
        """
        tags = self.properties.get(self.TAGS) or []
        for t in tags:
            if t[self.TAG_KEY].startswith('metering.'):
                # the user has added one, don't add another.
                return tags
        return tags + [{self.TAG_KEY: 'metering.groupname',
                        self.TAG_VALUE: self.FnGetRefId()}]

    def handle_delete(self):
        return self.delete_nested()

    def _get_conf_properties(self):
        conf_refid = self.properties[self.LAUNCH_CONFIGURATION_NAME]
        conf = self.stack.resource_by_refid(conf_refid)

        props = function.resolve(conf.properties.data)
        props['Tags'] = self._tags()
        return conf, props

    def _get_instance_definition(self):
        conf, props = self._get_conf_properties()
        return rsrc_defn.ResourceDefinition(None,
                                            SCALED_RESOURCE_TYPE,
                                            props,
                                            conf.t.metadata())

    def _get_instance_templates(self):
        """Get templates for resource instances."""
        return [(instance.name, instance.t)
                for instance in self.get_instances()]

    def _create_template(self, num_instances, num_replace=0,
                         template_version=('HeatTemplateFormatVersion',
                                           '2012-12-12')):
        """
        Create a template to represent autoscaled instances.

        Also see heat.scaling.template.resource_templates.
        """
        instance_definition = self._get_instance_definition()
        old_resources = self._get_instance_templates()
        definitions = template.resource_templates(
            old_resources, instance_definition, num_instances, num_replace)

        return template.make_template(definitions, version=template_version)

    def _try_rolling_update(self, prop_diff):
        if (self.update_policy[self.ROLLING_UPDATE] and
                self.LAUNCH_CONFIGURATION_NAME in prop_diff):
            policy = self.update_policy[self.ROLLING_UPDATE]
            pause_sec = iso8601utils.parse_isoduration(policy[self.PAUSE_TIME])
            self._replace(policy[self.MIN_INSTANCES_IN_SERVICE],
                          policy[self.MAX_BATCH_SIZE],
                          pause_sec)

    def _replace(self, min_in_service, batch_size, pause_sec):
        """
        Replace the instances in the group using updated launch configuration
        """
        def changing_instances(tmpl):
            instances = self.get_instances()
            current = set((i.name, i.t) for i in instances)
            updated = set(tmpl.resource_definitions(self.nested()).items())
            # includes instances to be updated and deleted
            affected = set(k for k, v in current ^ updated)
            return set(i.FnGetRefId() for i in instances if i.name in affected)

        def pause_between_batch():
            while True:
                try:
                    yield
                except scheduler.Timeout:
                    return

        capacity = len(self.nested()) if self.nested() else 0
        efft_bat_sz = min(batch_size, capacity)
        efft_min_sz = min(min_in_service, capacity)

        # effective capacity includes temporary capacity added to accommodate
        # the minimum number of instances in service during update
        efft_capacity = max(capacity - efft_bat_sz, efft_min_sz) + efft_bat_sz
        batch_cnt = (efft_capacity + efft_bat_sz - 1) // efft_bat_sz
        if pause_sec * (batch_cnt - 1) >= self.stack.timeout_secs():
            raise ValueError('The current UpdatePolicy will result '
                             'in stack update timeout.')

        try:
            remainder = capacity
            while remainder > 0 or efft_capacity > capacity:
                if capacity - remainder >= efft_min_sz:
                    efft_capacity = capacity
                template = self._create_template(efft_capacity, efft_bat_sz)
                self._lb_reload(exclude=changing_instances(template))
                updater = self.update_with_template(template,
                                                    self._environment())
                updater.run_to_completion()
                self.check_update_complete(updater)
                remainder -= efft_bat_sz
                if ((remainder > 0 or efft_capacity > capacity) and
                        pause_sec > 0):
                    self._lb_reload()
                    waiter = scheduler.TaskRunner(pause_between_batch)
                    waiter(timeout=pause_sec)
        finally:
            self._lb_reload()

    def resize(self, new_capacity):
        """
        Resize the instance group to the new capacity.

        When shrinking, the oldest instances will be removed.
        """
        new_template = self._create_template(new_capacity)
        try:
            updater = self.update_with_template(new_template,
                                                self._environment())
            updater.run_to_completion()
            self.check_update_complete(updater)
        finally:
            # Reload the LB in any case, so it's only pointing at healthy
            # nodes.
            self._lb_reload()

    def _lb_reload(self, exclude=None):
        '''
        Notify the LoadBalancer to reload its config to include
        the changes in instances we have just made.

        This must be done after activation (instance in ACTIVE state),
        otherwise the instances' IP addresses may not be available.
        '''
        exclude = exclude or []
        if self.properties[self.LOAD_BALANCER_NAMES]:
            id_list = [inst.FnGetRefId() for inst in self.get_instances()
                       if inst.FnGetRefId() not in exclude]
            for lb in self.properties[self.LOAD_BALANCER_NAMES]:
                lb_resource = self.stack[lb]

                props = copy.copy(lb_resource.properties.data)
                if 'Instances' in lb_resource.properties_schema:
                    props['Instances'] = id_list
                elif 'members' in lb_resource.properties_schema:
                    props['members'] = id_list
                else:
                    raise exception.Error(
                        _("Unsupported resource '%s' in LoadBalancerNames") %
                        (lb,))

                lb_defn = rsrc_defn.ResourceDefinition(
                    lb_resource.name,
                    lb_resource.type(),
                    properties=props,
                    metadata=lb_resource.t.get('Metadata'),
                    deletion_policy=lb_resource.t.get('DeletionPolicy'))

                scheduler.TaskRunner(lb_resource.update, lb_defn)()

    def FnGetRefId(self):
        return self.physical_resource_name_or_FnGetRefId()

    def _resolve_attribute(self, name):
        '''
        heat extension: "InstanceList" returns comma delimited list of server
        ip addresses.
        '''
        if name == self.INSTANCE_LIST:
            return u','.join(inst.FnGetAtt('PublicIp')
                             for inst in self.get_instances()) or None

    def child_template(self):
        num_instances = int(self.properties[self.SIZE])
        return self._create_template(num_instances)

    def child_params(self):
        return self._environment()


def resource_mapping():
    return {
        'OS::Heat::InstanceGroup': InstanceGroup,
    }
